My anubiases (is that a word?!) are all in gravel - regular gravel, not a special plant substrate. I have two petite nanas and a coffeefolia. I have a plant weight on them. I put the weight around the roots and not the rhizome. I try to tuck the weight into the gravel a bit so you can't see it as much, but it's still a little visible. The rhizome is right above the gravel, and some of the roots are as well. Some of the roots are very "curly" and some are growing straight up from the rhizome! I don't try to bend the roots too much. If some are sticking out of the gravel, that's ok. One of the petite nanas has two new leaves! I've only had it for two months.
I also cut the crypt pot away with scissors or a utility knife. I rinse under the faucet to get all the wool off. The roots can be very intertwined, and a lot of times I've separated the roots and found two, or three separate plants!
I have never had flourite so I wasn't sure if you also needed a root tab in the flourite. Thanks for clearing that up, Liz! A root tab would be very good for the crypt, Tom, and may help prevent melt. A good root system is beneficial too.
I know crypt melt can be puzzling. A few times, I've had a very long crypt root and I trimmed it a little. The crypt didn't melt. I've also moved crypts around two or three times and they were ok. Then one time, I turned the tank light off, but forgot about the room light. It was on until about 3-4 am. The next day all the crypts were melted. Only one came back.
How much floss is left around the crypt? If it's a lot, it may rot and cause some problems to the roots. Try to rinse it under the faucet and get as much out as you can. It's an additional disturbance to the crypt, but if the crypt has a lot of roots, the melting aspect should be diminished.